Method of obtaining a convenient opening device



June2, 1970 L. HOLTHAUS 1 3,515,777

METHOD OF OBTAINING A CONVENIENT OPENING DEVICE Filed Jan. 5. 1968 INVENTOR. R/C/7 oroQf/o/fh 0u5 nrroR/wfy' United States Patent 3,515,777 METHOD OF OBTAINING A CONVENIENT OPENHNG DEVICE Richard L. Holthaus, Midland, Mich., assignor to The Dow Chemical Company, Midland, Mich., a corporation of Delaware Filed Jan. 5, 1968, Ser. No. 695,923 Int. Cl. B29c 27/02 US. Cl. 264-27 6 Claims ABSTRACT OF THE DISCLOSURE A convenient opening device is taught in combination with a thermoplastic bottle wherein generally the opening device is of the tear string variety and comprises a current conducting wire embedded within the bottle wall. Specifically, such an opening device can be obtained by looping a length of wire about the neck of the bottle, applying a force to the two ends of the loop wire such that the intermediate or loop portion thereof is brought into intimate engagement with the surface of the neck, and placing a voltage across the two ends to electrically heat the wire to a temperature suflicient to melt the plastic adjacent the loop portion. The wire is maintained in a heated and tensioned condition a sufficient time to allow the melted plastic to fiow over and embed the loop portion of the wire within the neck wall. The two ends of the wire protrude from the embedded loop portion and serve as means to actuate the same as a tear string.

DESCRIPTION OF THE INVENTION A typical method of forming thermoplastic bottles wherein the bottle is formed, filled and sealed in the mold is illustrated in some detail in U.S. Pat. No. 3,251,915. Commonly, bottles formed in this manner are hermetically closed by pinching together their neck portions and securely sealing the same by the application of heat. As such, it has been usual in the past to open such bottles by means of a separate cutting device, as for example, a knife. Alternatively, and to provide a convenient Opening features, bottles of this kind can be sealed by a screw cap closure. Where a screw cap is employed, close fit is necessary between the bottle neck thread and the cap to obtain a hermetic seal. Leakage can be a problem with a closure of this type since a faulty seal can result if the required degree of thread tolerance is not maintained.

Accordingly, it is an object of the present invention to provide an improved opening device for thermoplastic bottles and the like wherein the opening device is such as to not disturb the leak proof qualities of the bottle.

Another object of the present invention is to provide a method for applying a leak-proof opening device to thermoplastic bottles which method is especially beneficial for usage on bottles of the kind formed, filled and sealed in the mold.

Briefly then, the present invention contemplates the provision of a convenient opening device for thermoplastic bottles and the like, and also a method of applying such an opening device to the bottle. Basically, what is provided is a tear string like arrangement with the tear string comprising a tensilely strong current conducting wire strategically embedded within the wall of the bottle, and with a portion of the Wire exposed for actuating the same. In a specific embodiment the opening feature is obtained by looping a length of wire about the neck of the bottle and applying force to the two ends of the wire to bring the loop portion thereof into intimate and pressing engagement with the surface of the neck, and placing a voltage across the two ends to electrically heat the wire "ice to a temperature suflicient to melt the plastic adjacent the loop portion. With the wire maintained in a heated and tensioned condition, a suflicient time is allowed for the melted plastic to flow over and embed the wire in the neck wall. The two ends of the wire protrude from the surface of the neck and serve as a means to activate the embedded wire as a tear string. Where a reclosable feature is desired, a stopped arrangement can be employed in combination with the above described opening device. The stopper preferably includes an outwardly extending flange overlying the upper rim of the neck and a plug fitted to the throat of the neck and positioned therein to close the same. Here the wire is applied be tween the overlying surfaces of the neck rim and the flange. As the heated wire proceeds inwardly, these two members are joined together by melted plastic thereby hermetrically sealing the bottle. Upon activating the embedded wire as a tear string, the joined portions of the stopper and neck are substantially rupturedsuch that the stopper can readily be removed from the throat of the neck to open the bottle. Replacing the stopper recloses the bottle after initial opening. Particularly, the present invention is adapted for employment on bottles formed, filled and sealed in the mold. Here the contents of the bottle can serve as a heat sink to cool the inner surface of the bottle such that the likelihood of the heated wire breaking through the wall thereof is minimized.

Other objects and advantages of the present invention and its details of construction will be apparent from a consideration of the following specification and accompanying drawings wherein:

FIG. 1 is a front elevational view of a thermoplastic bottle showing a first step in applying an opening device to the bottle in accordance with the principles of the present invention;

FIG. 2 is a fragmentary cross sectional view of the bottle of FIG. 1 after application of the opening device thereto;

FIG. 3 is across sectional view of the bottle of FIG. 2 taken along reference line 33 thereof; and

FIG. 4 is a view like FIG. 2 only showing a modified form of the invention.

Referring particularly to FIG. 1, there is shown a thermoplastic bottle or container 10 arranged in an upright position and including a hollow enclosed body portion 12, and a neck 14 integrally formed with the body portion 12 and extending upwardly therefrom. Neck 14 ineludes an inner channel or throat 18. Positioned atop neck 14 at its terminating end 17 is an integrally formed dome of peak 16 which closes off the inner channel 18 thereby sealing bottle 10. Contained within bottle 10 is a liquid product 20 as illustrated in FIG. 2.

The structure of the bottle 10 so far described is similar to the bottles of the known prior art. Specifically these bottles can be formed, filled and sealed while remaining in the confines of the mold, as, for example, by the method and apparatus taught in US. Pat. No. 3,251,- 915. Usually a polyvinyl chloride or polyethylene thermoplastic material is used to form these bottles.

The inventive concept pertains to the provision of a convenient opening device for bottle 10 wherein generally a tear string like arrangement is obtained by strategically embedding a length of wire within the wall of the bottle. The invention further pertains to a method of applying the wire to the bottle.

As shown in FIG. 1, a length of wire 22 is looped or fitted about the neck 14 of bottle 10 such that the wire 22 includes a generally circular shaped intermediate loop portion 24 located around neck 14, and two end portions 26 and 28 crossed over each other and extending generally tangentially from loop portion 24. While preferably the general plane of loop portion 24 substantially parallels the horizontal plane of neck 14, in FIG. 1 it is depicted at a slight angle therewith to better illustrate the invention. A force designated by the letter F is then applied to the two end portions 26 and 28 of wire 22 to intimately and pressingly engage the loop portion 24 of wire 22 and the outer surface 30 of neck 14. While the force F is being maintained, a voltage or potential is placed across the two end portions 26 and 28 causing a current to flow through and electrically heat wire 22. The wire 22 is heated in this manner to a temperature sufiiciently high to cause the plastic adjacent the loop portion 24 of wire 22 to enter a melted state. During the application of voltage across wire 22, it is important to maintain a suitable distance between the crossed portions 32 and 34 of end portions 26 and 28 such that electrical arcing or sparking is prevented from occurring thereat. Arcing or sparking between the end portions 26 and 28 at this location would tend to short out the loop portion 24 of the wire 22 making it diflicult to melt the plastic in the manner desired. With the Wire 22 maintained in its heated and tensioned condition, a sufiicient time is allowed for the melted and melting plastic to flow over and embed the loop portion 24 in the wall 36 of neck 14 without breaking through the inner surface 33 thereof. The voltage is then removed from across wire 22 and the force F usually for best results is maintained a short duration thereafter to allow the melted plastic to solidify about the embedded loop portion 24.

It is desirable to wet the inner surface 33 of neck 14 with the liquid product 20 prior to the heating of wire 22. Specifically, the area of wetting desired is that portion of inner surface 33 located opposite the points of application of wire 22 on the outer surface 30 of the neck 14. Wetting of inner surface 33 can, for example, be accomplished by shaking or jolting the bottle to agitate the liquid product therein. Preferably, however, the inner surface is wetted by turning the bottle 10 upside down for the duration of the heating step such that the neck 14 substantially fills with the liquid product 20. Accordingly, as the heated wire 22 approaches the wetted inner surface 33 of neck 14, the liquid product 20 effects a general cooling of the inner surface 33 thereby minimizing the possibility of a breakthrough by the heated wire 22.

As is illustrated in FIGS. 2 and 3, the looped portion 24 of wire 22 is embedded in the wall 36 of neck 14 with the two end portions 26 and 28 extending from the embedded looped portion 24. The wire 22 can be provided with a gripping means such as ring 38 securely affixed to end portion 26 as, for example, by mechanicall crimping the extension 37 of ring 38 to the end portion 26. Wire 22 embedded and arranged in this manner serves a tear string function in that upon application of suflicient force to one of the two protruding end portions 26 or 28 thereof, as, for example, by inserting a finger through ring 38 and pulling the exterior section 40 of wall 36 located adjacent the embedded wire 22 can be ruptured. With the exterior section 40 of wall 36 ruptured by wire 22, only an interior section 42 of wall 36 remains holding the neck 14 intact. The thickness and strength of the interior section 42 depends on the extent the looped portion 24 of wire 22 is embedded in wall 36. Preferably, the thickness of section 42 is adjusted with regard to the toughness of the material comprising bottle 10 such that a manual flexing or twisting of neck 14 by the eventual consumer as, for example, the average housewife, can effect a rupturing thereof allowing the upper portion 44 of neck 14 to be removed from bottle 10. The force required to rupture the inner section 42 can be tested, for

example, by periodically removing bottles 10 from production and opening them in a manner like that discussed above. If rupturing is deemed too diflicult, the extent the Wire 22 is embedded in wall 36 can be increased by heating the wire to a higher temperature such as by increasing the voltage applied thereto, and if desired increasing the force applied to end portions 26 and 28 and also the duration of wire is maintained ina heated and tensioned condition. This, of course, decreases the thickness of interior section 42 allowing for easier rupturing thereof.

Specifically, the wire 22 illustrated is of circular cross section and of less diameter than the thickness of the wall 36 of neck 14. Wires having cross sectional configurations other than circular, however, can be employed. For instance, a wire of a dew drop cross sectional configuration would be satisfactory. Here the tapered edge of the dew drop shaped wire would preferably be facing the exterior section 40 of wall 36 such that a sharp cutting edge results. This would allow for easier actuation of the opening device and would be especially suitable for thick walled containers wherein a substantial wall thickness would have to be ruptured to open the bottle. More specifically, the wire 22 selected must have suflicient tensile qualities such that the tensile force required to open the bottle 10 is not such that a failure of the wire 22 would result therefrom. Furthermore, while a generally good bond usually results between the wall 36 material and the embedded looped portion 24 of the wire 22, it is. conceivable in some applications that the wire 22 might slip out of the wall 36 rather than rupture its exterior section 40. If this problem is experienced, correction can i be had by using a serrated or similar wire having protuberances or the like extending outwardly from the surface thereof to securely lock into the wall 36 material.

As a specific example, a Nichrome wire 22 can be employed for the opening device of the present invention. The wire 22 can comprise a homogenous mixture of, for example, about 59.9 percent nickel, about 24 percent iron, about 16 percent chromium and about .1 percent carbon.

Particularly, Nichrome wire is desired for its good tensile strength and can be electrically heated. For a polyethylene bottle of about SO-mil wall thickness and l /z-inch diameter, neck 14, a 10-inch Nichrome wire of about 12- mil diameter and measuring generally about ll-ohm, resistance would be suitable. Here, to obtain the opening device of the present invention, the bottle 10 can first be turned upside down to wet the inner surface 33 of neck- 10 with the liquid product 20. With the bottle 10 in this position the Nichrome wire 22 is looped about neck 14 in the manner described above. A one pound force F-is then applied to the end portions 26 and 28 of wire 22..

to snuggly engage the looped portion 24 with the outer surface 30 of neck 14. The precise force F desired can be obtained by fixing the end portions 26 and 28 to a suitable weight and pulley apparatus. With the one pound force F being maintained, a twelve-volt potential is applied across the two end portions 26 and 28. For this purpose a twelve-volt battery can be employed with suitable low resistance lead wires connecting the two end portions 26 and 28 to the battery. The twelve-volt potential is applied for the duration of 8 seconds. After removing the voltage, the force F is maintained a few seconds or the time necessary to allow the melted plastic surrounding the embedded wire 22 to solidify.

Where a reclosability feature is desired, a stopper arrangement can be employed in combination with the above described opening device as, for example, one like that illustrated in FIG. 4. Here a stopper 46 is provided including a plug 48 fitted to and positioned within the throat 18a of neck 14a to securely close the same. Stopper 46 1 additionally includes a flange 50 integral with plug 48 t and extending outwardly from the top end 52 thereof to merge with the wall 36a of neck 14a. Embedded within 1 the merged portions 54 of wall 36a and flange 50 is the looped portion 24a of wire 22a.

The reclosability feature illustrated in FIG. 4 can be obtained by placing plug 48 of stopper 46. within throat 18a and then fitting the wire 22a about neck 14a so as to bisect the facing or overlying surfaces of the wall 360 and the fiange 50. As the heated wire precedes inwardly, the overlying surfaces of the flange 50 and wall 36a are joined together by melted plastic to hermetically seal bottle 10a. To insure bonding or joining of the flange 50 and wall 36a at the spaced crossed portions of the wire 22a, the bottle 1012! can be spun or turned a suitable angle during the heating and melting step such that the plastic is melted about the entire extent of the looped portion 24a. Also, here it might be desired to employ a wire coated with an electrical insulating material so that close spacing or possibly even contact can occur between the crossed portions of wire 22a without substantially shorting out the looped portion 24a. Specifically, the desired insulating material would be one that could elfectively electrically insulate the wire 22a without seriously effecting its heat dissipation qualities such that a melting of the plastic by electrical heating of the coated wire could be obtained.

While the present invention has been described in particular with regard to a Nichrome wire material, a number of other materials having the desired tensile and current conducting properties are well known and can be employed in the practice of the present invention. For example, a copper wire of sufficient cross sectional configuration to provide the necessary tensile strength can be employed for wire 22.

Furthermore, it is conceivable in some applications of the present invention that it would be desired to embed the wire in only a portion of neck wall rather than apply it about the entire circumference of the neck. For instance, by fitting the wire about the neck of the bottle such that the fitted wire assumes a generally U-shaped configuration, a hinged arrangement would result after initial opening of the bottle with the hinge comprising that portion of the circumference of the neck wall wherein the wire was not embedded.

I claim:

1. A method of applying an opening device to a thermoplastic bottle comprising:

fitting an electrical current conducting wire at least partially about a peripheral wall of said bottle;

said wire having a thickness dimensionless than the thickness of said wall;

applying a force to the two end portions of said wire to tension the wire and pressingly engage the intermediate portion thereof with the surface of said wall;

applying a potential across said two end portions to heat the wire to a temperature sufficient to melt the plastic adjacent the intermediate portion of said wire;

maintaining the wire in said heated and tensioned condition a sufiicient time to allow the intermediate portion of the Wire to become embedded within the wall of the bottle and without breaking through the inner surface thereof, and thereafter allowing the melted plastic to cool and solidify about the embedded intermediate portion of said wire.

2. The method of claim 1 wherein force is maintained on the two end portions during the cooling and solidifying step.

3. The method of claim 1 wherein the inner surface of said bottle in the vicinity of the application points of said wire is wetted prior to said heating step.

4. The method of claim 3 wherein said wire is fitted to the neck of the bottle by looping said wire about said neck such that the fitted wire comprises an intermediate portion about said neck, and two end portions crossed over each other and extending from said intermediate portion.

5. The method of claim 4 wherein said bottle is sealed and filled with a liquid product and wherein the inner surface of said neck is wetted by turning said bottle upside down prior to said heating step.

6. The method of claim 4 wherein said bottle includes a stopper comprising a plug fitted within the throat of said neck and a flange extending outwardly of said plug and overlying the terminating end of said neck, and wherein said wire is applied so as to interpose between the facing surfaces of said flange and said neck.

References Cited UNITED STATES PATENTS 1,428,185 9/1922 Reed. 1,447,059 2/ 1923 Benson. 3,265,781 8/ 1966 Peterson 264-27 ROBERT F. WHITE, Primary Examiner K. J. HOVET, Assistant Examiner US. Cl. X.R. 

